Inside Health

THE DOCTOR'S WORLD

THE DOCTOR'S WORLD; The Rewards, and the Roadblocks, of Medical Sleuthing

By LAWRENCE K. ALTMAN, M.D.

Published: May 1, 2001

ATLANTA, April 28—
The rewards of epidemiologic investigations include identifying new ways that old diseases can be transmitted, recognizing new health hazards and finding new ideas for reducing the incidence of preventable diseases. And although epidemiologists solve many outbreaks, they are stumped by others, or hampered in other ways, like hospital lawyers who do not allow them to interview affected patients.

Such rewards and frustrations were evident in reports by epidemiologists from the Centers for Disease Control and Prevention and state health departments at the 50th annual meeting of the Epidemic Intelligence Service here this week.

TULAREMIA -- Bioterrorism was a main reason that Dr. Katherine A. Feldman's team from the C.D.C. was summoned to investigate five cases of rabbit fever pneumonia on Martha's Vineyard last summer. One man had died. Rabbit fever, or tularemia, is caused by a bacterium that usually is transmitted by ticks and by handling animal carcasses. But the bacterium is ranked high on the list of biological warfare agents in part because inhaling the microbe is particularly dangerous and the death rate is high if antibiotics are not started early.

Dr. Feldman's team soon identified five more cases, all in men. Eight of the 10 had mowed lawns or cut brush. One had mowed over a rabbit. So the investigators donned protective clothing to collect tularemia bacteria in trapped mammals, and also re-created the mowing and collected samples of grass, air and water to show that such work can propel tularemia bacteria through the air to cause pneumonia.

Although a cluster of rabbit fever pneumonia cases occurred on Martha's Vineyard in 1978, tularemia cases have rarely been reported since then. But further investigation turned up a surprise: local doctors had detected a small number of cases of rabbit fever pneumonia over recent years but had not reported them to the health department as they were supposed to do. Flawed disease reporting had unnecessarily raised concerns of bioterrorism.

TYPHOID -- A classic epidemiologic investigative method is visiting the scene of an outbreak to seek clues to its cause and to interview patients and doctors. By such field work, Dr. Megan E. Reller's team from C.D.C. showed that an old disease, typhoid fever, could be transmitted in a new way.

About 400 cases of typhoid fever are reported each year in the United States. Most are contracted on foreign trips, usually through food or water contaminated by fecal matter.

Health officials were puzzled when four men who developed typhoid fever in Cincinnati reported no foreign travel or common meals. Through interviews Dr. Reller's team learned that the men were gay. By reviewing hospital records and alerting health officials in other states, the epidemiologists identified a total of nine cases in Cincinnati and Indianapolis. They found that one man was a typhoid carrier and that seven of the other eight patients said they had sexual relations with him before becoming ill. Dr. Reller's team concluded that the men acquired typhoid through fecal-oral transmission during sex.

Because the men cooperated poorly with her team, Dr. Reller said, she did not know how many other people were exposed.

SIDS -- Many important epidemiologic findings come from statistical analysis and small studies. For example, Dr. John A. Painter, an epidemiologist at the Louisiana state health department, reported new information about risk factors for sudden infant death syndrome, or SIDS.

The SIDS rate has fallen to about 8 per 10,000 live births in 1998 from about 15 in 1979. The drop has accelerated since 1992, when health officials began advising mothers to put their babies to sleep on their backs. But the rate appears to be leveling off, leaving SIDS as the leading cause of death (2,634 deaths in 1998) among infants from the second through 12th months of life in the United States.

The figures show that sleep position is not the only risk factor for SIDS. By studying SIDS cases in Louisiana, Dr. Painter found that exposure to smoking after birth and never having been breast-fed were important additional risk factors. To reduce the incidence, new public health efforts will be needed to promote breast-feeding and stress the dangers of smoking after birth as well as before delivery, Dr. Painter said.

CATERPILLARS -- Outbreaks, particularly unusual ones, are likely to be recognized only if doctors report cases to health departments. A case in point was an outbreak of severe itching from hives and rash among Boy Scouts at a camp in New Mexico last summer, Dr. John T. Redd said. The symptoms were from a venom produced by caterpillars that were abundant at the camp.

The first clue came when an allergist called the New Mexico health department to report the case of a 10-year-old Boy Scout who was asthmatic and had gone to an emergency room four times because of persistent itching and wheezing after he returned home to El Paso. The boy and his mother asked whether his symptoms might be from the caterpillars, not asthma.

The allergist then looked up articles that pointed Dr. Redd's team to exposure to caterpillars of the Douglas fir tussock moth (Orgyia pseudotsugata) that are widely distributed through the western United States. Dr. Redd's investigation showed that the allergic reactions occurred more commonly at certain camp sites, affecting as many as 55 percent of the scouts. For a number of reasons, Dr. Redd's team is advising the scouts not to play a game in which they they put caterpillars on the forearm, allow them to crawl on to the index finger, then flick the insects into a fire.

FLU VACCINE -- Epidemiologic studies can determine whether adverse reactions result from a drug or vaccine or only from a particular manufacturer or batch.

Dr. Eleni Galanis from Health Canada in Ottawa reported that epidemiologists traced the adverse reactions to one influenza vaccine that was made and distributed only in Canada. Health Canada officials publicized the problem. They also allowed the manufacturer's 3.8 million doses to continue to be administered because they thought the life-saving benefits of the vaccine outweighed its relatively mild risks.

Many participants from the United States, including experts in influenza and vaccines, first learned of the problem here and expressed surprise that United States officials had not informed them about a significant problem with a standard vaccine. They were disturbed because the C.D.C.'s widely publicized plan to give flu shots to 75 million people in this country over the winter was significantly delayed by different manufacturing problems.

A spokeswoman for C.D.C. said the centers did not report the problem in its weekly report because the implicated Canadian vaccine was not distributed in the United States and officials did not want to discourage Americans from getting a flu shot.

Meeting participants criticized the Canadian decision to continue using the implicated vaccine, saying that if a similar problem was found in an influenza vaccine in this country, its use would be suspended. While the Canadian manufacturer seeks to find the cause of the adverse reaction, Dr. Galanis said Canadian officials were concerned that administering the flu vaccine next season to those who experienced reactions last winter could lead to more serious, even life-threatening, reactions.

BIRTH DEFECTS -- Even when epidemiologists confirm the existence of an outbreak, the solution may be beyond their grasp, as illustrated by Dr. Dana C. Crawford's investigation of birth defects in Dickson County, Tenn., 30 miles west of Nashville. Dr. Crawford's team identified 18 babies with cleft lips and palates from January 1997 through October 2000, five times the expected rate, but they found no clear explanation.